Spectroscopic Ellipsometry (SE) was developed in the early 1970's after single wavelength ellipsometry had gained widespread acceptance. The first (SE) systems provided limited Ultraviolet (UV) to near Infrared (IR) spectral range capability, and with the exception of a few research instruments, this remained the case until the 1990's. Many challenges faced development of Vacuum Ultraviolet (VUV) ellipsometer systems, including the fact that many optical element materials absorb in the (VUV) wavelength range. Vacuum Ultraviolet (VUV) ellipsometry was so named as it was initially carried out in vacuum, however, the terminology is today applied where purging gas such as nitrogen or argon is utilized in place of vacuum at wavelengths which typically have an energy less than about 10 ev. The reason (VUV) ellipsometry must be carried out in vacuum or purging gas is that (VUV) wavelengths, are absorbed by oxygen and water vapor.
In the mid-1980's a Spectroscopic ellipsometer was constructed at the BESSY Synchrotron in Berlin for application in the (VUV) wavelength range, (eg. 5–35 eV), and in the 1990's Spectroscopic ellipsometry was achieved in the Extreme Ultraviolet (EUV) range, (eg. greater than 35 eV), at KEK-PF. Application of ellipsometry in the (VUV) and (EUV) wavelength ranges remained restricted to said research facilities until in 1999 commercial (VUV) ellipsometer systems became available from companies such as the J.A. Woollam Co. Inc. At present there are approximately twenty-five (25) Vacuum Ultraviolet Systems in use worldwide. It is noted that commercial (VUV) instruments, which provided wavelengths down to 146 nm, were introduced in response to the need for means to investigate material properties at 156 nm, which is utilized in lithography as applied to semiconductor gate oxide production.
A known patent which provides for use of VUV wavelength electromagnetic radiation through 10 eV is U.S. Pat. No. 6,414,302 B1 to Freeouf.
Continuing, it is important to appreciate that a typical ellipsometer system comprises:                a. a source of a beam electromagnetic radiation;        b. a polarizer element;        c. optionally a compensator element;        d. optional additional element(s);        e. a stage for supporting a sample system;        f. optional additional element(s);        g. optionally a compensator element;        h. an analyzer element; and        i. a detector system.Spectrophotometer systems delete the polarizer, analyzer and compensators, and the detector system can comprise either a single detector element or a plurality of detector elements. It is also noted that the combination of the source of a beam electromagnetic radiation and the polarizer element and the optional compensator element is often referred to as the Polarization State Generator, while the combination of the optional compensator element analyzer element and detector system is often referred to as the Polarization State Detector.        
The practice of ellipsometry, polarimetry, spectrophotometry, reflectometry, scatterometry and the like, using Visible, Infrared (IR), (eg. 2–33 micron), and Ultraviolet (UV), (eg. 135–1700 nm), Electromagnetic Radiation Wavelengths, then is, as disclosed above, known. As mentioned, electromagnetic Radiation with wavelengths below about 190 nm is absorbed by atmospheric components such as Oxygen and Water Vapor. Thus, practice of Ellipsometry etc. using UV Wavelengths is typically carried out in vacuum or an atmosphere which does not contain oxygen and/or water vapor or other absorbing components. The J.A. Woollam Co. VUV-VASE, (Registered Trademark), for instance, utilizes a substantially enclosed Chamber which encompasses a substantially enclosed space which during use is purged by Nitrogen and/or Argon or functionally equivalent gas. (Note Nitrogen does not significantly absorb UV Range wavelengths, and Argon is in some respects even a better choice). It is noted that the J.A. Woollam Co. VUV-VASE has proven to provide good data in cases even when operated without Nitrogen or Argon purging, and has been applied to obtain reflection data using an electromagnetic beam caused to approach a sample system at a normal or oblique angle of incidence, transmission data with an electromagnetic beam being caused to approach a sample system at a normal or oblique angle of incidence, either using unpolarized electromagnetic radiation, partially polarized electromagnetic radiation or polarized electromagnetic radiation. That is very good data has been obtained utilizing unpolarized; partially polarized, randomly polarized; linearly polarized; with respect to a sample system linearly “p” polarized; with respect to a sample system linearly “s” polarized; and circularly polarized electromagnetic radiation in purged and atmospheric ambients.
The source of the electromagnetic radiation in the J.A. Woollam CO. VUV-VASE is preferably a Deuterium Lamp and/or a Xenon Lamp, which produce wavelengths of 115–400 nm, (of which 135–190 nm is used), and up to about 2000 nm, respectively. Specific wavelengths are selected by a J.A. Woollam Co. Monochromator which is a Cherny-Turner type Spectrometer sequentially comprising, mounted inside an enclosing means;
a) source means for providing of a beam including ultraviolet wavelength range electromagnetic radiation;
b) a first slit;
c) a first spherical mirror;
d) a first stage comprising a plurality of gratings, each of which can be rotated into a functional position;
e) a second spherical mirror;
f) a second slit;
g) a third spherical mirror
h) a second stage comprising a plurality of gratings, each of which can be rotated into a functional position;
i) a forth spherical mirror; and
i) a pin hole;
there further being a beam chopper means present after said source means and typically just before said pin hole.
In use an electromagnetic beam from said source of the electromagnetic radiation is:                caused to pass through said first slit;        reflect from said first spherical mirror;        interact with one of said plurality of gratings on said first stage which is rotated into a functional position;        reflect from said second spherical mirror;        pass through said second slit;        reflect from said third spherical mirror;        interact with one of said plurality of gratings on said second stage which is rotated into a functional position;        reflect from said forth spherical mirror; and        exit through said pinhole;and at some point in said progression be subjected to chopping.The gratings on said first and second stages are rotated into precise desired functional positions via stepper motors, separately controlled by computer. This has proven to provide superior precision and repeatability than commercially available grating positioning systems. Further, an electromagnetic radiation beam produced by said Monochromator has been shown to provide a highly collimated beam, with typical defining parameters being a 5 mm diameter at the pinhole output of the Monochromator, with divergence to about 20 mm diameter at 20 Feet, (ie. 6000 mm). This represents a divergence angle of only about 0.00125 radians, (ie. 0.07 Degrees).        
In use, the monochromator system is utilized to provide a sequence of substantially single wavelengths which are applied to a sample system at least one angle of incidence, and while typically can be present anywhere between the source of a beam electromagnetic radiation and the detector in an ellipsometer system, is in the standard J.A. Woollam Co. VUV-VASE, for example, positioned directly after the source of a beam electromagnetic radiation.
It must be also appreciated that an alternative approach to obtaining data using monochromator systems, which apply only a substantially single wavelength at a time to a sample system, is to apply a multiplicity of wavelengths simultaneously and obtain data from each thereof simultaneously, but again, where the wavelength range includes wavelengths which are absorbed by oxygen and/or water vapor, the system must be placed into a substantially enclosed space into which is flowed purging gas. The J.A. Woollam Co. M2000, (Registered Trademark), is a relevant example of a Rotating Compensator Ellipsometer System, as described in U.S. Pat. No. 5,872,630 is incorporated herein by reference. Said 630 patent is a CIP from U.S. Pat. No. 5,666,201, which describes applying dispersing means to present numerous wavelengths to different detector elements simultaneously, in not only Rotating Compensator, but also Rotating Analyzer and Rotating Polarizer Ellipsometer Systems. Said 201 patent is further incorporated by reference hereinto. The 630 patent discloses a spectroscopic rotating compensator material system investigation system comprising a source of a polychromatic beam of electromagnetic radiation, a polarizer, a stage for supporting a material system, an analyzer, a dispersive optics and at least one detector system which contains a multiplicity of detector elements, said spectroscopic rotating compensator material system investigation system further comprising at least one compensators) positioned at a location selected from the group consisting of:                before said stage (STG) for supporting a material system (MS);        after said stage (STG) for supporting a material system (MS); and        both before and after said stage (STG) for supporting a material system (MS).        
When said spectroscopic rotating compensator material system investigation system is used to investigate a material system present on said stage for supporting a material system, said analyzer and polarizer are maintained essentially fixed in position and at least one of said at least one compensators) is caused to continuously rotate while a polychromatic beam of electromagnetic radiation produced by said source of a polychromatic beam of electromagnetic radiation is caused to pass through said polarizer and at least one of said compensator(s). Said polychromatic beam of electromagnetic radiation is also caused to interact with said material system, pass through said analyzer and interact with said dispersive optics such that a multiplicity of essentially single wavelengths are caused to simultaneously enter a corresponding multiplicity of detector elements (DE's) in said at least one detector system.
The J.A. Woollam Co. Rotating Analyzer VASE (Registered Trademark), system, as described in U.S. Pat. No. 5,373,359, provides another example of such a system. Here-to-fore the J.A. Woollam CO. systems which utilize multiple detector element detectors have not been applied in purged substantially enclosed spaces.
It is noted that an ellipsometer or polarimeter system of the disclosed invention can involve selecting at least one detector system from the group consisting of:                photo-diode;        photo-diode array;        charge-coupled-device;        photo-multiplier tubes;        photo-resistive elements;        photo-conductive elements;        thermo-piles;        bolemeters; and        having detector system distinguishing aperturing present.        
Of particular importance to the disclosed invention is that inconveniences have been identified with, for instance, application of the described J.A. Woollam Co. VUV-VASE monochromator system in that outgassing of UV wavelength absorbing materials from such as wiring and electronic components etc., (purging of which is required), can require annoying periods of time. This problem is somewhat overcome by providing the J.A. Woollam Co. VUV-VASE a two-speed purge control means such that a sequestered subspace can be purged quickly and then sustained at a slower speed once purging is substantially complete, a Nitrogen conserving slower maintenance purge speed can be effected. And new monochromator design presently being developed, which provides less outgassing components therewithin, also promises to reduce purging time. A time delay, however, still exists between the beginning of purging and sufficient completion thereof, during which data can not be obtained using wavelengths which are absorbed by oxygen and water vapor, and this slows down data acquisition. Regardless of the ellipsometer system involved, while such a time delay can be minimized, it can never be eliminated. The disclosed invention provides methodology for optimizing use of time during data procurement wherein wavelengths applied to a sample system include those absorbed by oxygen and/or water vapor and wavelengths which are not so absorbed, comprising obtaining data using the later wavelengths during evacuation or purging.
In view of the state of the art, there remains need for methodology which can be practiced with either Monochromator or Dispersion based Polychromatic Ellipsometer, Polarimeter, Reflectometer, Spectrophotometer and the like systems which operate in a controlled ambient atmosphere inside a substantially Enclosed Space containing Chamber, (eg. to enable elimination of Oxygen and Water Vapor), using wavelengths both in and outside ranges in which said wavelengths are absorbed and not absorbed by oxygen and/or water vapor. The disclosed invention provides methodology for optimizing use of time during data procurement wherein wavelengths utilized include those absorbed by oxygen and/or water vapor and wavelengths which are not so absorbed.